Retractile cords



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RETRACTILE CORDS Filed Aug. 24, 1959 2 Sheets-Sheet 2 United StatesPatent "ice p 3,003,018 RETRACTILE CORDS John Brown Cook, North Haven,Conn., nsslg'nor to The Whitney Blake Company, Hamden, Conn., acorporation of Connecticut Y Filed Aug. 24, 1959, Ser. No. 835,769 3Claims. (Cl. 174-69) This invention relates to retractile cords suitablefor use in various appliances, such as telephones, coffee pots and thelike in which the appliance ismoved from time to time, and in which theretractile cord is designed to take up the slack and avoid the unsightlyappearance incident to the use of ordinary cords or iacketed conductors.t

The term cord refers to one or more conductors, such as one ormorelengths of llexiblecopper wire, which are enclosed within a jacketformed of suitable insulating material, to provide what is oftenreferred to as a jacketed conductor. A retractile cord is a cord ofhelical shape andelastic,: to'the end that the helical cord will returnto its original position after extension. f

It is an object of the present invention to provide a retractile cord ofgreater compactness, that is, one in which the helix, when retracted, isshorter with respect to its extended length than in the casefof theusual retractile cord.

According to this invention, the conductors of the retractile cord arearranged side by side in a plane which is generally perpendicular to theaxis ofthe helix, thus providing a jacketed conductor which isribbon-like or flat in appearance. In the usual multi-conductor type ofeach other thus providing a cord of improved appearance. r'

Still another object is to provide a retractile cord of improvedretractile properties.

Accordingto the present invention, .the inner portion of the jacketedconductor is crimped in a sinusoidal manner so that the alternate ridgesand depressions will nest in the corresponding ridges and depressions ofadjacent convolutions. Furthermore, this crimping substantiallyincreases the extensibility over a fiat retractile cord which'is notcrimped, and at the same time improves the retractile properties of thecord.

In the ordinary retractile cord wherein the jacket is in circular crosssection, the retractile properties are, generally speaking, a functionof the diameter of the helix with respect to the diameter of thejacketed conductor,

the lower the diameter ratio, the greater being the resilience of thehelix. As a result, the ratio of extensibility is generally of the orderof 4 or 5 to l.

By making an uncrimped at retractile cord structure having an increaseddiameter ratio, the ratio of Yextensibility can be increasedsubstantially since,in theory, the extended length would be the uncoiledlength of the innermost element, which is to say, the product oftheinner diameter, the number of convolutions, and pi. Actually however,this result cannot be obtained since the uncrimped flat configurationprevents the convolution'y from unwinding with the result that theratio` of extensibility is more of the order ofk 10 or 12 to l.

However, I have found that by crimping the inner portion of eachconvolution, that the extensibility can be very considerably increased;as a matter of fact, in certain n 3,003,018 lPatented Oct. 3, 1961diameter ratios, or proportions of helix diameter to jacket i width, thecord is extensible to a length in excess of the theoretical butunattainable maximum indicated above, which is the function of the innerdiameter of the helix, and that this increased extensibility kisattained without introducing additional winding stresses in the cord.,

A further object of my invention is to provide` vfor a portableappliance orthe like an improved storage ar rangement so thatthe'appliance and the cord will prt?r sent a neat and self-containedappearance; a A

Other objects, features and advantages will become apparent as thedescription. proceeds.

With reference nowy to the drawings in which like reference numeralsrepresent like parts:

FIG. 1 is a side elevation of an appliance `which ine corporates a`preferred embodiment of my invention;

FIG. 2 isa plan view of FIG. 1; I 1 j FIG.\3 is an elevation of theretractile cord of FIG. l in its retracted position; ,y

FIG. 4k is aplan view'of FIG. 3;

FIG. 5 is a section taken along line 5-5 of FIG. 4'; AFIG. 6 is anelevation `of the retractile cord in its extended position; and i FIG. 7is a section showing a modification. j

In FIGS. l and 2 an-appliance such ras a telephone instrument 10 isshown which comprises a basell and a hand set 12 which is removablyreceived by a cradle 13. The hand set is electrically connected to thebase 11 by a retractile cord 14 having an upper end portion 15, a lowerend portion 16 andan intermediate portion17 in the form of a helix.Although the end portions 15 and 16 may also be of the helical form tobe described here inafter, it is preferable lto so manufacture the cordthat these arestraight anduncrimpcd as shown in FIGS. l and 2.

` Ther retractile cord 14 rests on a platform 28 which projectsoutwardly from the base 11, and a suitable piu 19 may projectupwardlyfrom the base through the helix 17 in order to facilitate thestacking of the core by its own resilience when the hand set 12 isreturned to its cradle 13.

As shown in FIG. 5, the retractile cord .14 comprises a plurality ofmetallic conductors which are arranged side by side in ar commonplane,'four conductors 20, 21, 22 and 23 being shown for the purpose ofillustration. The conductors are maintained in their side b'y sideposition and insulated from each other .by ra jacket 24 which provides acord of ribbon like appearance which could be described as flat, exceptfor the crimps 26. The conductors 20 to 23 may each be provided withlindividual jackets, not shown, in the customary manner,

ing the rdesired retractile .or resilient properties. Ani

example of a suitable .jacket composition is vsetforth in co-pendingapplication of Edgar L. Love, Serial No.

659,698, tiled VMay 16,' 1957,'together withy the curingkcharacteristics thereof. Where individual jackets 'are `also providedthese may be of a suitable resin or rubbery like composition, or even offabric, according to the usual practice in the jacketed conductor art.

The cord is extruded in straight or uncoiled form so that for a givensection the length of all of the metallic conductors r20 to 23 is thesame. Therefore, when the cord'is wound into a helix wherein the generalplane of the conductors of each convolution is substantiallyperpendicular to thel axis of the helix, the inner cords 20, 21 and 22will tend to buckle.

According to my invention, the inner portion 25 of the cord` isprovidedwith crimps 26 which take up the excess length ofthe innercordsy in the jacket, the crimps providing both improved retractileproperties and facilitating the stacking of the cord.

n VT he crimps are of similar shape and are equidistantly epaced fromeach other so'that when in contracted form the crimps of one convolutionwill nest with the crimps of adjacent convolutions. The crimps areapplied both to the metallic conductors Ztl to 23 and to the jacket 24so that the insulation thickness will be substantially uniform. Thecrimping is done after the cord has been extruded and as it is beingplaced on a suitable mandrel for curing. The mandrel preferably is agrooved mandrel the inner portions of the grooves being also crimped soas to insure that the crimps in the jacket will be maintained duringcuring, to the end that the jacket is given a set both in the helicalform and in the crimped form.

By virtue of the fact that the uncrimped length of the inner conductorsis equal to the length of the outer conductor 23 the ratio ofextensibility is considerably increased over that of an uncrirnped flatcord which is extruded in helical form. In the latter instance, ofcourse, the maximum theoretical extension length is the uncoiled lengthof the innermost conductor. However, as pointed out above, this degreeof extensibility cannot be attained because the innermost filament ofthe helix tends `to maintain the same radius of curvature with theresult that the extensibility is limited to that which arises from thetorsional flexure of the jacketed cord.

However, when the flat cord is crimped, as in the present invention,additional extension is provided by the fact that the crimped innerfilament permits an un- Winding or an increase in the radius ofcurvature.

As an example, the helix of FIGS. 3 and 4 may have an outer diameter of2% inches, an inner diameter of "1% inches, and a convolution thicknessof approximately .'15 inch. A coil comprising 51/6 convolutions can beextended to 341/2 inches which is to be compared with a theoreticalextension of 28 inches in an uncrimped iiat coil, as determined by theinner diameter, and with a theoretical'maxirnum of 381/2 inches if theouter filament is taken as controlling, or 361/2 inches if the length ofthe outer conductor 23 is taken as controlling.

The 341/2 inches of extension is about double the extension that can beattained without the crimping, where the extension is limited to thetorsional deformation of the cross section of the cord. In other words,the additional unwinding action that is permitted by the crimping addsabout 100% to the extension.

Furthermore, since this additional extension results in a iiattening ofthe crimps, which represents either an elongation of the inner filamentof the jacketed material or a flexural deformation of the cross section,the crimping in itself introduces an element of Velasticity resulting inimproved retractile properties.

Therefore, the present invention provides not only increased ratio ofextensibility, but also an improvement in retractile properties.Furthermore, as pointed out above, the crimps provide a means of nestingthe convolutions with respect to each other so as to provide a -helix orstack which will retain its right cylindrical configuration of uniformdiameter, thus providing a much neater appearance than if the crimpswere not present.

The advantages of the present invention can be obtained with either'agreater orlesser number of metallic conductors. However, the retractileproperties of the cord are primarily a function of the size, shape andproportions of the jacket material and of the helix, with the resultthat the location of the one or more conductors within the jacket crosssection does not affect the results obtained. In other words, where onlytwo conductors are necessary, these two conductors could be conductors22 and 23 or 20 and 21, or any other combination of the four conductorsshown, the other two being eliminated. This is not to say that the widthor the proportions of the jacket may not be varied according to thenumber of conductors provided in the jacket, but, as a general proposition, I have found that a flat crimped cord provides a very definiteadvantage over the cord of circular cross section of the prior art.Where more than one conductor is required, the desired jacket crosssection is best obtained by disposing the conductors in side by siderelationship.

Although my improved retractile cord is of utility and variousapplications, as indicated above, it is of particular utility inconnection with an appliance such as a telephone, coffee pot, clock, andthe like in which the selfstacking characteristics of the cord may beutilized by providing a definite location for the cord when retracted,or for that portion Vof the cord which is retracted. in the applicationillustrated, the base of the telephone provides a platform for theYreception of the cor-d. In the case of certain other appliances,however, as shown in FIG. 7, a bell-shaped base 3d, of a lamp, forinstance, is provided Which provides -a cavity 3i for the reception of atlwo conductor appliance cord 32 which is manufactured in accordancewiththe principles of this invention, the plug end 33 of the cord extendingoutwardly through a slot 34 in the base, and the unused portion of thecord resting on the table 35 or other surface on which thev applianceitself is supported, the helix 32 being concealed by the bell-shapedbase. ln such an arrangement, the free or plug end of the cord can beeither at the top or the bottom of the helix.

' Although only a preferred embodiment of my invention has been shownand disclosed herein it will be understood that various modificationsand changes can be made without departing from the scope of theinvention as pointed outby the appended claims.

I claim:

l. A retractile cord comprising a plurality of parallel conductorsvaligned side by side, a jacket surrounding same to provide a flat,jacketed cord, said cord being arranged in a helix the axis of whichisperpendicular to the general plane of the cord, and the inner edges ofthe convolutions being crimped toprovide indentations which registerwith the indentations of adjoining convolutions so that said.convolutions will nest within each other.

2. A retractile cord comprising a metallic conductor covered by a jacketformed of a cured elastomer, said cord being arranged in helical shape,and being at in cross section, with the iiatness of the cord being in aplane substantially perpendicular to the axis of the helix, the innerportionsof said cord being crimped lto permit a partial unwinding of thehelix in vorder to provide in creased extensibility.

3. A retractile cord comprising a plurality of metal conductors ofuniform length aligned side by side in parallel relationship, a jacketformed of a cured elastomer surrounding same to provide a flat jacketedcord, said cord being arranged in a helical shape With the plane of saidconductors approximately perpendicular to the axis of the helix, theinnermost one of said conductors and that portion of the jacket whichsurrounds the same being crimped so as to permit elongation of saidinnermost conductor and its surrounding jacket when said helix isextended, the crimping of said jacket imparting resilience to saidretractile cord when extended.

References Cited in the le of this patent UNITED STATES PATENTS1,865,069 Allen June 28, 1932 2,609,417 Cox et al. Sept. 2, 19522,678,779 Bellmer May i8, 1954 2,704,782 Ames Mar. 22, 19,55

y FOREIGN PATENTS 762,343 Great Britain Nov. 28, 1956 1,155,793Y FranceDec. 2, 1957

